JP2651352B2 - Photocathode, phototube and photodetector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocathode, a phototube, and a photodetector, and more particularly, to obtaining one-dimensional or two-dimensional information such as an incident position and an incident light image for weak light. Related to light detection technology.

[0002]

2. Description of the Related Art As a general device for detecting light containing one-dimensional or two-dimensional position information on weak light, there is a device configured by combining an image intensifier and a solid-state imaging device. In this device, photoelectrons are excited by photons incident on the photocathode from the input window of the envelope,
Photoelectrons emitted from the photocathode into a vacuum are focused and accelerated by an electron lens system, then imaged by a phosphor and converted again into an optical signal to enhance light. The enhanced optical signal is photoelectrically converted again by a solid-state imaging device such as a CCD, and the position information is extracted as an electric signal.

In addition, there is a photomultiplier tube having a position detecting function. In this example, the position information is obtained by dividing and multiplying the anode of the photomultiplier tube and performing photodetection. Another example in which a photomultiplier tube has a position detecting function is disclosed in Japanese Patent Application Laid-Open No. 60-20441.

In this photomultiplier tube, a photocathode is formed on the inner wall surface of a face plate. A mesh electrode is provided between the photocathode and a focusing electrode for forming an electric field for guiding photoelectrons emitted from the photocathode to the first-stage dynode. The mesh electrode is formed from the photocathode to the photocathode and the focusing electrode. Are disposed only on one side at a position at a distance of about 1/10 of the distance between. Then, an electric field distribution is formed that gradually prevents photoelectrons from reaching the first-stage dynode from one side to the other side. By applying the bias voltage to the mesh electrode, one of the photoelectrons emitted from the entire photoelectron emission surface of the photocathode is prevented from reaching the first dynode. That is, the trajectory of the photoelectrons is changed, and only those emitted from a predetermined portion of the emission surface are multiplied and output as electric signals. Based on the output signal level and the level of application of the bias voltage to the mesh electrode, light detection with positional resolution is performed by an external determination device. Thus,
Position detection is performed by detecting only photoelectrons excited by light incident on a specific position and not disturbing the trajectory.

[0005]

In a conventional example in which an image intensifier and a solid-state image pickup device are combined, it is essentially unavoidable to convert from an optical signal to an electric signal to an optical signal to an electric signal. Efficiency deteriorates due to loss, etc., and performance decreases.

In a photomultiplier tube having a divided anode, crosstalk between the photocathode and the multiplier and between the multiplier and the anode becomes a problem, and the positional resolution is not essentially improved.

In a photomultiplier tube having a mesh electrode interposed therebetween, only a part of the photoelectrons emitted from the entire photoelectron emission surface of the photocathode is detected at the time of measurement to detect the position. There is an inherent problem in terms of ratio. Further, since the position resolution is also determined by changing the trajectory of the photoelectrons, crosstalk increases structurally, and only one photomultiplier tube can determine only about two positions. Conversion is inherently difficult.

Accordingly, an object of the present invention is to realize a photocathode having a position detecting function with little crosstalk, and a phototube and a photodetector using the same.

[0009]

The photocathode of the present invention includes a photoelectric conversion layer in which photoelectrons are excited by incident photons. Photoelectrons generated and accelerated inside the photoelectric conversion layer are emitted from the photoelectron emission surface. A semiconductor layer to be emitted outside,
A surface electrode formed on the semiconductor layer on the photoelectron emission surface and a back electrode formed on the surface opposite to the photoelectron emission surface so as to face the surface electrode, and the surface electrode is divided to form a plurality of pixel electrodes. The pixel electrodes are electrically insulated from each other, and the plurality of pixel electrodes are connected to a plurality of bias application wirings that independently apply a positive bias potential compared to the back electrode.

The phototube of the present invention includes a vacuum vessel, a photocathode disposed inside the vacuum vessel, and an anode disposed inside the vacuum vessel and receiving photoelectrons emitted from the photocathode, The photocathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, a semiconductor layer that emits photoelectrons generated and accelerated inside the photoelectric conversion layer from the photoelectron emission surface to the outside, and a photoelectron emission surface. And a back electrode formed on the semiconductor layer opposite to the photoelectron emission surface so as to face the front electrode. The front electrode is divided into a plurality of pixel electrodes and The plurality of pixel electrodes are electrically insulated, and the plurality of pixel electrodes are connected to a plurality of bias application wirings for independently applying a positive bias potential compared to the back surface electrode. A plurality of switch elements for individually switching bias application by individually turning on and off a connection between a wiring and a plurality of pixel electrodes, a switching circuit for individually turning on and off a plurality of switch elements, and a plurality of switch elements. Switching control means having a plurality of switching wires for individually connecting a plurality of output terminals of the switching circuit to each control terminal is provided, and at least one of the plurality of stem pins led out of the vacuum vessel to the outside is provided. A book is connected to the back electrode, at least one is connected to the bias application wiring, at least two are connected to the input terminal of the switching circuit, and at least one is connected to the anode.

The photodetector of the present invention includes a phototube having a photocathode and an anode inside a vacuum vessel, a power supply for applying a potential to the photocathode and the anode, timing control means, and memory means. The photocathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, a semiconductor layer that emits photoelectrons generated and accelerated inside the photoelectric conversion layer from the photoelectron emission surface to the outside, and a photoelectron emission layer. A surface electrode formed on the surface semiconductor layer, and a back electrode formed on the semiconductor layer opposite to the photoelectron emission surface so as to face the surface electrode. The surface electrode is divided into a plurality of pixel electrodes. And a plurality of pixel electrodes are electrically insulated from each other, and the plurality of pixel electrodes are connected to a plurality of bias applying wires that independently apply a positive bias potential compared to the back electrode, and further, inside the vacuum vessel, A plurality of switch elements for individually switching bias application by individually turning on and off a connection between a plurality of bias application lines and a plurality of pixel electrodes, and a plurality of switch elements individually A switching circuit for turning on and off the switching circuit, and a plurality of switching wires for individually connecting a plurality of output terminals of the switching circuit to respective control terminals of the plurality of switching elements. The switching circuit sequentially switches on and off the plurality of switching elements in response to the timing pulse, and the memory means starts a storage operation when a start signal is given. The output of the anode is stored in correspondence with the positions of the pixel electrodes which are sequentially in a state capable of emitting photoelectrons based on the timing pulse.

[0012]

According to the photocathode of the present invention, the surface electrode is divided to form a plurality of pixel electrodes, and these pixel electrodes are configured so that the bias potential is applied independently. Only those pixels that are generated can emit internally generated photoelectrons to the outside. Therefore, when the pixel electrodes are arranged in a one-dimensional array, a one-dimensional position dividing ability can be realized, and when the pixel electrodes are arranged in a two-dimensional matrix, a two-dimensional position dividing ability can be realized.

According to the photoelectric tube of the present invention, since the vacuum vessel has the above-described photocathode and the switching control means for switching the application of the bias to the plurality of pixel electrodes, the one-dimensional or two-dimensional one is provided. A phototube having a positional resolution of?

According to the photodetector of the present invention, in addition to the photoelectric tube and the power supply, a timing control unit and a memory unit are provided. The timing control means stores the output of the anode in the memory means in accordance with the position information of the pixel electrode in the photoelectric tube in a state capable of emitting photoelectrons. Can be stored in the memory means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, a semiconductor layer 100 as a main body of the photocathode 1 is formed by forming InGaAs on an InP substrate 101.
A light absorption layer 102 is formed, and an InP contact layer 103 is formed thereon. An ohmic electrode 104 made of Au (gold) or the like is provided on the back surface of the InP substrate 101.
Is formed as a back electrode, and the InP contact layer 103 is formed.
A Schottky electrode 105 made of Al (aluminum) or the like is formed as a surface electrode on the surface. Here, the ohmic electrode 104 is formed thin or has a large number of openings so as to transmit incident light, and the Schottky electrode 105 is divided into pixel electrodes 105 ₁ , 105 arranged in a one-dimensional array. ₂ , ..., 105 _n . Each pixel electrode is patterned into a mesh, and photoelectrons can pass through the openings. InP
Of the surface of the contact layer 103, especially the openings of the mesh-shaped pixel electrodes are coated with a thin layer of Cs (cesium) or the like for lowering the work function of the surface. Is easily released.

As shown in FIG. 1, such a photocathode 1 is attached to a vacuum vessel 21, and an anode 22 is provided at a position facing the photocathode 1. Each of the pixel electrodes 105 ₁ ,
105 ₂ ,..., 105 _{n
1, 106 2, ..., 106} n are connected, which are connected to the power supply terminal 301 via a switch SW. on the other hand,
Although the ohmic electrode 104 is connected to the power supply terminal 302, the terminal 301 has a higher positive potential than the terminal 302. For this reason, the terminal 301 is set by the switch SW.
Pixel electrodes 105 _{1 to} 105 to which a bias from
Only _n has a higher positive potential than the ohmic electrode 104, and the opening and the photoelectron emission surface in the vicinity thereof are in a state where photoelectrons can be emitted. The photoelectrons emitted in the vacuum travel toward the anode 22. This is because the anode 22 is more positively biased via the power supply terminal 303.

As shown in FIG.
When the detection light (hv) is transmitted through the substrate and is incident, the light is photoelectrically converted in the InGaAs light absorption layer 102 having a narrow band cap to generate photoelectrons (-e). At this time, if a bias is applied between the ohmic electrode 104 and the Schottky electrode 105, photoelectrons are accelerated in the semiconductor layer 100 in the direction of the photoelectron emission surface as shown in the lower diagram to obtain high energy. Released in vacuum (level VL). Therefore, the bias is applied to the individual pixel electrodes 105 _{1 to} 105 _n obtained by dividing the Schottky electrode 105 by the switch SW.
By turning on and off individually, photoelectrons generated inside the InGaAs light absorbing layer 102 can be emitted from the photoelectron emission surface to the outside of the semiconductor layer 100, that is, into a vacuum, only for the pixel electrode for which the switch SW is turned on. .

In the photocathode of FIG. 3, the pixel electrodes form a one-dimensional array and are fixed to a holder. The long semiconductor layer 100 is fixed to a ceramic holder 401, which is fixed to a molybdenum mold 402, and the semiconductor layer 10.
0 and the mold 402 are insulated. The mold 402 terminal pins 403 _1, 403 _2, 403 _3, 403 ₄ is fixed through an insulator, pin 403 ₁ a positive bias power supply +
Is connected to V _B on the semiconductor layer 100 of the biasing line (not shown), the pin 403 ₂ is connected to ground (the ground) to the ohmic electrode 104 on the semiconductor layer 100,
Pin 403 _3, 403 ₄ is connected to the input terminal of the shift register 5 on the semiconductor layer 100. Here, the shift register 5 is switching control means for sequentially applying a bias to the pixel electrodes 105 _{1 to} 105 _n.
3 _3, 403 ₄ via the start pulse SP and clock pulse CLK to be described later is input. The semiconductor layer 10
The surface other than the photoelectron emission surface of No. 0 is covered with an insulating film 120 such as SiO ₂ .

The pixel electrodes 105 _{1 to} 105 _n in FIG.
When the −1, i, i + 1-th are expressed in perspective, FIG.
It is shown as follows. That is, the pixel electrode 105 _i
Is patterned into a mesh having 15 openings, having a switching element S _i of the field effect transistor (FET) in the corners. Then, its gate electrode connected to the i-th output terminal of the shift register 5 by an Al wiring 501 _i. Therefore, when a pulse is input from the shift register 5 via the Al wiring 501 _i , the i-th switching element _Si is turned on and the bias application wiring 1
A bias + V _B is applied from 06 _i to the pixel electrode 105 _i . Such an operation is performed for 1 to i−1, other than the i-th one.
The same applies to the i + 1 to n-th pixels.

As shown three-dimensionally in FIG. 5, an ohmic electrode 104 and each of the pixel electrodes 105 _{1 to} 105
_{Between n} , diodes D _{1 to} D _n having the ohmic electrode 104 as a cathode are equivalently formed. By turning on the switch S ₁ to S _n are output from the shift register 5, the diode D ₁ of the respective pixel ~D
_n becomes reverse bias individually. Then, due to the electric field inside the semiconductor layer 100 under the reverse bias, the photoelectrons are accelerated in the direction of the pixel electrode 105 as shown in FIG. 2 to obtain high energy and are emitted to the outside of the semiconductor layer 100.
Note that a clock pulse CLK is input to the input terminal 502 of the shift register 5, and a start pulse SP is input to the terminal 503.

The operation in this case will be described with reference to FIGS. Here, the light detection outputs at the respective pixels corresponding to the pixel electrodes 105 _{1 to} 105 _n are _denoted by P _{1 to} P _n . The outputs P _{1 to} P _n are taken out as the output A _OUT of the anode 22 when configured as shown in FIG. As shown in FIG. 7, a start pulse SP is provided for activating the shift register 5, and when this pulse SP is provided, the shift register 5 receives pulses from the output terminals 501 _{1 to} 501 _n in response to the clock pulse CLK. is output, thereby, switching element S ₁ to S _n formed of FET is sequentially turned on, sequentially bias + V _B is applied to each pixel electrode 105 ₁ to 105 _n. Thus, a photoelectron emission sequentially state from each pixel, the output P ₁ to P _n are sequentially taken out to the outside as the anode output A _OUT.

Referring to FIG. 8, a photodetector using the photocathode according to the above embodiment will be described. As shown,
A transmission-type photocathode 1 is attached to an input window of the vacuum vessel 21, and a switching control unit 50, an anode 22, and a dynode 25 for multiplying photoelectrons by two-dimensional electrons are provided therein. The power supply 61 supplies an anode potential + V _A to the anode 22 through a stem pin penetrated through the vacuum vessel 21, supplies a dynode potential V _D to the dynode 25, and supplies a bias potential + V _B to the switching control unit 50. The timing control unit 62 outputs a start pulse SP in accordance with an instruction of an operator or the like, and outputs a clock pulse CL having a constant cycle.
K is continuously output. The signal processing circuit 63 amplifies the anode output A _OUT , performs threshold processing for removing noise, or performs analog / digital conversion, and supplies an output signal to a storage device 64 with a controller such as a microprocessor. The display device 65 is connected to the storage device 64.

In this configuration, the timing control unit 62
Outputs the start pulse SP from the switching control unit 5
0 and the storage device 64 are activated, and each operates in response to the clock pulse CLK. That is, the switching control unit 50
Each time a clock pulse CLK is input, a pulse is sequentially output from an output terminal corresponding to each pixel electrode, and each pixel is sequentially brought into a state capable of emitting photoelectrons. The photoelectrons emitted in this manner are multiplied by the dynode 25 and supplied to the storage device 64 via the signal processing circuit 63.

At this time, since the clock pulse CLK is also supplied from the timing control unit 62 to the storage device 64, the controller of the storage device 64 outputs the anode output A in accordance with the count value of the clock pulse CLK.
_OUT is stored so as to correspond to the position of the pixel in a state capable of emitting photoelectrons. For example, the count value of the clock pulse CLK is used as an address, and the value (digitally converted value) of the anode output A _OUT is stored as data. Such processing can be understood from the timing chart of FIG. The sequential on / off switching of all the pixel electrodes is repeated a plurality of times, and the pixel output is stored in the storage area corresponding to the position of the pixel in the storage device 64 while adding the anode output _AOUT for each pixel. The image data of the detected light is obtained. This image is C
It is displayed on a display 65 provided with an RT or the like.

FIG. 9 shows a photocathode according to another embodiment, wherein the upper side is a top view, the center is a side view partially showing a cross section, and the lower side is a bottom view. An InGaAsP light absorption layer 102 and an InP contact layer 103 are formed on the InP substrate 101 by epitaxial growth, and an Au ohmic electrode 104 is formed on the back surface of the InP substrate 101. A plurality of Al Schottky electrodes 105 to be joined are formed in a pattern. Here, the semiconductor layer 100 including the substrate 101, the light absorbing layer 102, and the contact layer 103 may have a heterojunction structure of GaAs and AlAs or a mixed crystal thereof, such as Ge (germanium) and Si (silicon), or A heterojunction structure composed of a mixed crystal of Schottky electrode 1
05, for example, Al, Au, Ag (silver), W
(Tungsten), Ni (nickel), Ti (titanium), or an alloy thereof.

The pattern of the Schottky electrode 105 may be a mesh-like electrode composed of orthogonal linear members as shown in FIG. 9, or a pattern as shown in FIG. In FIG. 10, the upper figure shows a pattern of a mesh-like electrode having hexagonal openings, the middle figure shows a stripe pattern of a grid-like electrode made of parallel members, and the lower figure shows a comb-like pattern. Is shown. In each case, the openings through which photoelectrons pass are spaced at about 10 μm or less. The light may be incident through the back surface, that is, through the ohmic electrode 104, or may be incident through the front surface, that is, through the opening of the Schottky electrode 105. When light is incident from the back surface, the ohmic electrode 104 is formed of a translucent material, or is formed of a metal film sufficiently thin enough to transmit light,
Alternatively, it is formed from a metal film having a large number of openings through which light can pass.

In FIG. 9, each pixel electrode 105
Corresponding to ₁ to 105 _n are formed in the vicinity of the switch S ₁ to S _n of the FET, on the bias voltage to the electrode 105 ₁ to 105 _n by the switching function of the FET, off is performed. The surface of the photoelectron emitting surface is thinly coated with Cs (cesium) for lowering the work function of the surface. Such coating materials are alkali metals or compounds thereof, oxides or fluorides of alkali metals. Alkali metals include K in addition to Cs
(Potassium), Na (sodium) Rb (rubidium)
Is included. The substrate 101 is fixed by a ceramic holder 401, and the surface thereof is an Al Schottky electrode 105.
Is covered with an insulating film 120 of SiO ₂ or SiN, except for the portion of.

Further, in the example of FIG. 9, on the semiconductor layer 100 is a shift register 5 comprising a transistor is formed, the gate of the FETS ₁ to S _n are wired to the n output terminals of the shift register 5, respectively ing. The shift register 5 generates a scanning pulse in response to a start pulse SP and a clock pulse CLK from the outside, and generates a scanning pulse for each of the FETs S ₁ to S ₁ .
S _n sequentially turned on so with the Al Schottky electrode 105 ₁
Address 105 _n . The terminals 403 ₁ , 403
Reference numeral ₄ denotes a connection between the circuit on the substrate 100 and an external circuit.
Terminal 403 _3, 403 ₄ are for signals input to the shift register 5, the terminal 403 _1, FETS ₁ ~
It is also the order to provide a bias voltage + V _B from the outside to the Schottky diode D ₁ to D _n through S _n.

FIG. 11 shows a configuration example in which the photocathode of the embodiment is applied to a head-on type photomultiplier.
The upper side is a schematic view of the face plate viewed from the inside, and the lower side is a sectional view of the envelope 21 in the axial direction. It is assumed that n = 6 for the sake of space. A ceramic holder 402 for fixing a semiconductor substrate as a photocathode is fixed to a metal fitting 405 made of molybdenum by spot welding, and an electrode terminal 403 is connected outside the face plate. A focusing electrode 26 is provided inside the vacuum vessel, that is, the envelope 21, and eight stages of dynodes 25 _{1 to} 25 ₈ are provided.
Are arranged. An anode 22 is provided in front of the _ninth reflective dynode 259. In this photomultiplier tube, six sets of terminal pins 403 are provided corresponding to each of the six pixels, and the pixels that can emit photoelectrons are switched by the output of an external control circuit.

In the photomultiplier tube shown in FIG. 12, the control circuit includes a shift register 5 provided on a face plate 405.
Has been realized. The input of the start pulse SP and the clock pulse CLK to the shift register 5 is realized by the stem pin 406.

In each of the embodiments shown in FIGS. 11 and 12, a transmission type photocathode, that is, photoelectrons are emitted in the same direction as the photon incidence direction (therefore, the photon incidence surface is opposite to the photoelectron emission surface). Type photocathode is used. The embodiment of FIG. 13 uses a reflection-type photocathode, that is, a photocathode of a type in which photoelectrons are emitted in a direction opposite to the photon incidence direction (therefore, the photon incidence surface is the same as the photoelectron emission surface). Such a photomultiplier tube is called a side-on type, and the cross-sectional structure is shown in FIG. Photons incident from a vacuum container 21 such as glass pass through a focusing electrode (mesh electrode) and enter the photocathode 1. The emitted photoelectrons are multiplied by dynodes 25 _{1 to} 25 ₈ ,
The light enters the anode 22.

The operation of the photomultiplier tube shown in FIGS. 11, 12, and 13 can be described with reference to the timing chart shown in FIG. 7, "S ₁ to S _n" are from the shift register indicates the output level to the FET switch, the switch is turned on when that is high. Start pulse SP
There shift register 5 starts the operation by a high level, sequential FET operates switch S ₁ to S _n are turned on by the clock pulse CLK. Switch S ₁ ~
S _n on the pixel electrode 105 ₁ to 105 _n to a predetermined bias voltage is applied light emission surface of the (or bias voltage applied Schottky diode) is operated.
Of course, at this time, the Schottky electrode to which no bias voltage is applied does not operate as a photoelectron emission surface, so that photoelectrons are not emitted regardless of the presence or absence of incident light. “P _{1 to} P _n ” in FIG. 7 indicate the bias voltages of the respective photoelectron emitting surfaces, and are active when high.

It is assumed that P _{3 on the} photoemission surface of the photomultiplier tube is
Assuming that light enters the portion, photoelectrons are emitted when a bias voltage is applied to the portion. Photoemission surface P
The trajectory of the photoelectrons emitted from ₃ is corrected by the focusing electrode, and is incident on the first dynode. The first-stage dynode generates and emits secondary electrons several times larger than the incident primary electrons (photoelectrons), and these secondary electrons are multiplied by a second-stage dynode, a third-stage dynode, and finally multiplied by 10 ^It reaches about ^six times and is detected by the anode 22 as a photocurrent.

Since the photoelectron emission surfaces P _{1 to} P _n are sequentially operated by the address signal from the shift register 5, photoelectrons from each part of the photoelectron emission surface are multiplied and detected as a photocurrent. By synchronizing the clock pulse CLK input to the shift register 5 with the signal read by the anode 22, the anode output A _OUT becomes the photoelectron emission surface P
₁ to P ₆ have been either light emission from the position of the throat is determined. Therefore, the anode output A _OUT and the clock pulse CL
From the timing of K, one-dimensional position information on incident light can be obtained.

Here, an example has been described in which the shift register 5 is formed on the same substrate as the photoelectron emission surface and the switching and addressing of the FETs are performed. However, as shown in FIG. Can be controlled directly without using the shift register 5. If the wiring is not complicated, the shift register 5 can be formed outside the semiconductor substrate forming the photocathode.

The operation of the photomultiplier tube shown in FIG.
This is the same as the eleventh photomultiplier tube. P of photoelectron emission surface_Three
If light enters the portion, the shift register 5
Photoelectron emission surface P by address signal₁~ P₆Operate sequentially
The photoemission surface P _ThreePhotoelectrons emitted from
The trajectory is modified by the focusing electrode and becomes the first stage dynode
Incident. Number of incident primary electrons at the first dynode
Double secondary electrons are generated and emitted, and these secondary electrons are
Dynode, 3rd stage dynode ...
0⁶Approximately doubled and detected as photocurrent at anode 22
Is done. Therefore, the clock input to the shift register 5 is
Pulse CLK and the signal read by the anode 22 are synchronized
As a result, the anode output becomes₁~
P₆From which position the photoelectron is emitted.

Further, the present invention can be applied to a side-on type photomultiplier, and FIG. 13 shows an example of the configuration in that case. Reflective photoelectron emission surface having a one-dimensional position detecting function is provided at the light hν is made incident, as in the embodiment described above, the resulting photoelectrons dynode 25 21 _to
5 ₈ are multiplied by the detected by the anode 22. Although the direction in which the photoelectrons are emitted is different from the above-mentioned transmission type photoelectron emission surface, the operation method is exactly the same as that of the head-on type.
According to the present invention, position detection using a reflection-type photoelectron emission surface, which has been impossible in the related art, can be performed.

FIG. 14 shows an embodiment of the present invention of a photoelectron emission surface when the photoelectron emission surface is configured to have a two-dimensional position detecting function. This embodiment has a configuration in which a plurality of (m rows) are arranged in the vertical direction in FIG. 14 when the above-described one-dimensional position detection function is provided. Further, although not included in FIG.
A shift register for addressing in the vertical direction is formed outside (left side in the figure). That is, the pixel electrodes 10 of each row
5 _{11 to} 105 _1n , 105 _{21 to} 105 _2n , ..., 105 _m1 to
M shift registers 5A _{1 to} 5A corresponding to 105 _mn
m is formed on the substrate 100 on which the photocathode 1 is formed.
In addition, each of the bias application lines 106 ₁ to 106 m
An external shift register is connected to 6 _m via a terminal pin. Here, the first shift register 5A ₁ to 5 A _m is inputted from the outside through the respective terminal pins clock pulse CLK and a start pulse SP,
There are n output terminals corresponding to each pixel electrode. A second shift register provided externally also receives CLK and SP, and outputs a photocathode arranged in a two-dimensional matrix of m rows and n columns of pixel electrodes.

FIG. 15 shows an equivalent circuit for operating the m × n pixel-type photoelectron emission surface shown in FIG. 14, and a portion surrounded by a dotted line is a circuit formed on the substrate shown in FIG. Is shown. First shift register 5A in the horizontal direction
_1, 5A _2, ..., 5A _m has the same circuit configuration as in FIG. 2, the start pulse SP and clock pulse CLK ₂
Totally and sequentially turns on the switches S ₁₁ to S _mn operate in parallel simultaneously by. The switches SB _{1 to} SB _m are provided so as to be connected to the output of the second shift register 5B in the vertical direction.
It becomes successively on being addressed by the shift register 5B by the clock pulse CLK _1. Shift register 5A
_1, 5A _2, ..., switch S provided at the output of 5A _m
11 to S _mn, the switch SB against the bias source + V _{B
1 to} SB _m in series, and an external bias voltage + V _B is applied to the Schottky diodes D _{11 to} D _mn when both switches in series with the power supply are turned on.

A photomultiplier tube having a two-dimensional position detecting function can be constructed in the same manner as the one-dimensional case using the photoelectron emission surfaces of FIGS. FIG. 16 is a timing chart showing the operation of the photomultiplier tube in this case. “S” in FIG. 16 indicates the output level from the shift register to the FET switch, and when high, the switch is on.

When the start pulse SP goes high, all shift registers start operating simultaneously.
The shift register 5 by an input clock pulse CLK ₁
The FETs in the column B are sequentially turned on, and first, the switch SB ₁
Is addressed and turned on. The clock pulse CLK _2, rows of shift registers are also operated in parallel at the same time. When none of the outputs of these shift registers is set to high, given the bias voltage + V _B, and an optical emission plane P ₁₁ to P _mn adapted to emit photoelectrons. In the timing chart of FIG.
₁₁ is on, the vertical switches S _{21 to} S
_2m is also turned on, if the switch SB ₁ is turned on, the bias voltage + V _B given only to the light emission surface P _11, this works. When the switch SB ₁ is turned on, turned sequentially on one of the vertical direction in the switch S ₁₁ to S _mn, it operates sequentially photoelectron emitting surface P ₁₁ to P _1n. These are sequentially switches SB ₂ , SB ₃ ,.
This is also performed for SB _m .

The clock pulse CLK ₁ by synchronizing the shift register A ₁₁ to A _mn clock pulse CLK _2, and by the width of the clock pulse CLK ₁ is to be n times the period of the clock pulse CLK _2, Schottky diode P ₁₁
To P _mn from the upper left to the lower right of the figure in order of bias voltage + V _B
Switch to give And, from the upper left to the lower right of the figure, the photoelectron emitting surfaces P _{11 to} P _mn are sequentially _arranged.
The photoelectrons generated by the excitation of the incident light are emitted from, and are multiplied and detected.

As in the previous embodiment, the clock pulse C
By synchronizing the read signal with LK ₁ and the clock pulse CLK ₂ , two-dimensional position information on incident light can be obtained. Therefore, the clock pulse CLK
It is possible to two-dimensional position detection by synchronizing the _1, CLK ₂ and the anode output. Of course, as described above, the shift register or the FE for switching is used.
T may be formed on the same substrate as the photoelectron emission surface, or may be formed on other portions.

As shown in FIG. 17, the first and second shift registers may all be formed on a substrate 100 forming a photocathode. By doing so, the number of terminal pins on the substrate 100 can be significantly reduced, so that the positional resolution can be improved as a multi-pixel. In addition, each symbol in FIG.
The same reference numerals are used for the same elements as 4 and 15.

FIG. 18 shows an example of a configuration system of an optical position detecting device using the above-described photomultiplier according to the present invention. This system includes a photomultiplier tube PMT, a drive circuit unit for driving the same, a readout circuit unit 82 for reading out signals, a DC power supply unit 81 for supplying a high voltage to the photomultiplier tube PMT, Input clock pulse (CLK, CL) to the photomultiplier tube PMT
K ₁ , CLK _2, etc.)
3. An A / D converter 84 for reading signals from the photomultiplier tube PMT, an oscilloscope (or a display device such as a CRT or LCD) 85, and a control computer 86. Other than the photomultiplier tube PMT, a conventional one is used. As described above, the timing of generating the input clock pulse to the photomultiplier tube PMT is controlled by the computer 86, and the signal read out from the photomultiplier tube PMT is fetched to obtain the position of the light incident on the photomultiplier tube PMT. Information can be easily obtained, and it is also possible to form an image and display it on a display device.

As described above, the photoelectron emission surface of the present invention is
Despite having a photoelectron emission surface formed on one substrate, it is possible to operate as a plurality of independent photoelectron emission surfaces by individually applying a bias voltage to each of the plurality of pixel electrodes. Therefore, it is possible to realize a photodetector capable of detecting a position with much less crosstalk with a much simpler structure than a conventional photodetector having a photoelectron emission surface.

The photoelectron emission surface of the present invention enables ultra-sensitive and low-noise light detection by multiplying secondary electrons of photoelectrons, so that position detection and image information detection under weak light can be easily performed. It can be carried out. Furthermore, since a portion to which no bias voltage is applied does not emit electrons due to dark current, no noise is generated from a portion which does not operate as a photoelectron emission surface, so that the photodetector is essentially very low noise. Therefore, the photodetector using the photoelectron emission surface according to the present invention and a photodetector using the photodetector have an ultra-high sensitivity, and
Low-noise position detection becomes possible.

Conventionally, a photoelectron emission surface having this type of position detection function had to be essentially a so-called transmission type structure in which the direction of light incidence and the direction of emission of photoelectrons were different. However, according to the present invention, a position detecting function can be provided even in a so-called reflective structure in which the direction of light incidence and the direction of emission of photoelectrons are the same, and the degree of freedom in device structure and design is greatly expanded.

According to the present invention, instead of selecting and multiplying photoelectrons from the entire surface of a photoelectron emission surface for photoelectrically converting incident light,
A part of it functions by applying a bias voltage. Therefore, it is possible to easily obtain a photoelectron emission surface having a position detection function with low noise and very little crosstalk. In addition, a photodetector having an ultra-sensitive position detecting function can be realized by adding a multiplying unit to form a photomultiplier.

The present invention is not limited to the above-described embodiment, but can be variously modified. For example, the main material of the photoelectron emission surface is I
Although the description has been made using nP and InGaAsP, the present invention is not limited to this. Further, the Schottky electrode, ohmic electrode, alkali metal and the like are not limited to those used in this embodiment. Further, by using the shift register as an address decoder and separately applying an input address pulse, it is possible to detect a position where random access is possible.

By the way, US Pat.
143 "discloses an example of a photoelectron emission surface that accelerates photoelectrons using an internal electric field and emits the electrons into a vacuum.
However, position information cannot be obtained from the photoelectron emission surface described in this document. Also, see Japanese Patent Application Laid-Open No. 4-26941.
FIG. 9 "shows a photoelectron emission surface in which a Schottky electrode is formed in a pattern. However, this also does not similarly form a plurality of electrodes and does not individually apply a bias voltage. Location information cannot be obtained.

[0053]

As described above, according to the photomultiplier of the present invention, it is possible to obtain a detection output corresponding to the incident position of light on the photocathode, and to make the photomultiplier compact and compact. By using the photoelectron emission surface of the present invention, the above-described photomultiplier can be configured. Further, according to the photodetector using the photomultiplier tube of the present invention, one-dimensional or two-dimensional information on the incident light can be obtained even if the incident light on the photocathode is weak. .

[Brief description of the drawings]

FIG. 1 shows a photocathode according to an embodiment and a phototube having the same, wherein the upper part is a top view of the photocathode, and the lower part is a vertical cross-sectional view of the phototube taken along line X ₁ -X ₁ in the upper part.

FIG. 2 shows an energy band structure of the photocathode of FIG. 1, in which the upper side shows a state where no bias voltage is applied, and the lower side shows a state where a bias voltage is applied.

FIG. 3 is a perspective view showing a photocathode assembly according to the embodiment.

FIG. 4 is a perspective view illustrating an example of a pattern of a pixel electrode in the embodiment.

FIG. 5 is a diagram three-dimensionally showing an equivalent circuit of the photocathode of the embodiment.

FIG. 6 is a plan view showing an equivalent circuit of the photocathode of the embodiment.

FIG. 7 is a timing chart showing the operation of the embodiment.

FIG. 8 is a diagram illustrating a photodetector using a photocathode according to an embodiment.

FIG. 9 is a top view, a side view, and a bottom view showing the photocathode assembly of the embodiment.

FIG. 10 is a top view showing another example of the pixel electrode of the embodiment.

FIG. 11 is a view showing a head-on type photomultiplier using a photocathode of an example.

FIG. 12 is a diagram showing a head-on type photomultiplier using a photocathode of an example.

FIG. 13 is a view showing a side-on type photomultiplier using a photocathode of an example.

FIG. 14 is a diagram showing an embodiment in which a two-dimensional matrix is formed.

FIG. 15 is a diagram showing an embodiment in which a two-dimensional matrix is formed.

FIG. 16 is a timing chart showing the operation of the original embodiment.

FIG. 17 is a diagram showing another embodiment in a two-dimensional matrix.

FIG. 18 is a block diagram illustrating a photodetector according to an embodiment.

[Explanation of symbols]

100 semiconductor layer, 104 ohmic electrode (back surface electrode), 105 Schottky electrode (front electrode), 5 shift register, 21 vacuum container, 22 anode, 25 dynode.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneo Weihara 1126, Nomachi, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Inside (72) Inventor Masami Yamada 1126, 1126, Ichinomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Corporation (72) Inventor Norio Asakura No. 1126, Nomachi, Hamamatsu-shi, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. Tomoko Suzuki, 1126 No., Ichinomachi, Hamamatsu City, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (56) References JP-A-62-299088 (JP, A) JP-A-62-157631 (JP, A) International publication 91/14283 ( WO, A)

Claims (21)

(57) [Claims] 1. A semiconductor layer comprising: a photoelectric conversion layer for exciting photoelectrons therein by an incident photon; and a semiconductor layer for emitting the accelerated photoelectrons generated and accelerated inside the photoelectric conversion layer from a photoelectron emission surface to the outside; A surface electrode formed on the semiconductor layer on the emission surface; and a back electrode formed on the semiconductor layer on the surface opposite to the photoelectron emission surface so as to face the surface electrode. The plurality of pixel electrodes are electrically insulated from each other, and the plurality of pixel electrodes are respectively connected to a plurality of bias application wires that independently apply a positive bias potential compared to the back electrode. A photocathode characterized by the following. 2. The photocathode according to claim 1, wherein said semiconductor layer has a heterojunction structure. 3. The photocathode according to claim 2, wherein said semiconductor layer has a heterojunction structure of GaAs, AlAs, or a mixed crystal thereof. 4. The photocathode according to claim 2, wherein said semiconductor layer has a heterojunction structure of InP, GaAs, or a mixed crystal thereof. 5. The photocathode according to claim 2, wherein said semiconductor layer has a heterojunction structure of Si, Ge or a mixed crystal thereof. 6. An alkali metal, a compound of an alkali metal, or an oxide or fluoride thereof, is applied on the photoelectron emission surface of the semiconductor layer, wherein the alkali metal is Cs, K, Na, or Rb. The photocathode according to claim 1, wherein 7. The photocathode according to claim 1, wherein said semiconductor layer and said front electrode are in Schottky contact, and said semiconductor layer and said back electrode are in ohmic contact. 8. The photocathode according to claim 1, wherein the plurality of pixel electrodes are arranged in a one-dimensional array or a two-dimensional matrix. 9. The photocathode according to claim 1, wherein the surface electrode has an electron transmitting portion for passing the photoelectrons generated in the photoelectric conversion layer and accelerated in the semiconductor layer and emitting the photoelectrons to the outside. . 10. The method according to claim 1, wherein the surface electrode is made of Al, Au, Ag,
2. The photocathode according to claim 1, comprising W, Ti, Ni, WSi or an alloy thereof. 11. The photocathode according to claim 1, wherein said surface electrode has a number of openings through which said photoelectrons can pass. 12. The photocathode according to claim 1, wherein the surface electrodes form a stripe, mesh or grid pattern having a pitch of 10 μm or less. 13. The back electrode is made of a translucent material, is a metal electrode that is thin enough to transmit incident photons, or is a metal electrode that has a large number of openings that can transmit incident photons. 2. The photocathode according to 1. 14. The semiconductor device, wherein the photoelectric conversion layer is formed on a semiconductor substrate, and a plurality of bias application wirings respectively provided on the semiconductor substrate so as to correspond to the plurality of pixel electrodes, respectively. 2. The photocathode according to claim 1, wherein a plurality of switch elements for individually switching bias application by individually turning on and off the connection between the bias application wiring and the plurality of pixel electrodes are formed. 15. A switching circuit for individually turning on and off the plurality of switching elements on the semiconductor substrate, and a plurality of output terminals of the switching circuit individually connected to respective control terminals of the plurality of switching elements. 15. The photocathode according to claim 14, wherein a plurality of switching wirings are formed. 16. The photocathode according to claim 15, wherein said switch element is a transistor, and said switching circuit is a shift register having an output terminal connected to a gate terminal of said transistor. 17. The plurality of pixel electrodes are arranged in a two-dimensional matrix with m rows and n columns (m and n are integers of 2 or more), and the plurality of switch elements are arranged in the m rows and n columns of pixels. M provided for each electrode and connected in parallel for each row
xn first switches, and m second switches connected in series with each of the n first switches in each row, and the switching circuit comprises: M shift registers, each of which has n output terminals connected to the control terminals of the n first switches in each row, and m m second switches. A second terminal in which m output terminals are connected to the control terminal of
16. The photocathode according to claim 15, comprising a shift register. 18. A photovoltaic device comprising: a vacuum vessel; a photocathode disposed inside the vacuum vessel; and an anode disposed inside the vacuum vessel and receiving photoelectrons emitted from the photocathode. The cathode includes a photoelectric conversion layer that internally excites photoelectrons by incident photons, a semiconductor layer that emits the photoelectrons generated and accelerated inside the photoelectric conversion layer from the photoelectron emission surface to the outside, and the photoelectron emission surface. A surface electrode formed on the semiconductor layer, and a back electrode formed on the semiconductor layer opposite to the photoelectron emission surface and opposed to the surface electrode, wherein the surface electrode is divided. Forming a plurality of pixel electrodes and being electrically insulated from each other, the plurality of pixel electrodes being connected to a plurality of bias application lines for independently applying a positive bias potential compared to the back electrode, Further, inside the vacuum container, a plurality of switch elements for individually switching bias application by individually turning on and off the connection between the plurality of bias application wirings and the plurality of pixel electrodes; A switching control means having a switching circuit for individually turning on and off the switching elements, and a plurality of switching wires for individually connecting a plurality of output terminals of the switching circuit to respective control terminals of the plurality of switching elements. At least one of the plurality of stem pins led out of the vacuum vessel is provided on the back electrode, at least one is provided on the bias application wiring, and at least two are provided on the input terminal of the switching circuit. And at least one is connected to the anode. 19. The photoelectric tube according to claim 18, wherein said photoelectric conversion layer is formed on a semiconductor substrate, and said switching control means is formed on said semiconductor substrate. 20. The phototube according to claim 18, further comprising electron multiplying means for multiplying photoelectrons emitted from the photocathode by two-dimensional electron multiplication inside the vacuum vessel. 21. A phototube having a photocathode and an anode inside a vacuum vessel, a power supply for applying a potential to the photocathode and the anode, timing control means, and memory means, wherein the photocathode comprises: A semiconductor layer including a photoelectric conversion layer for exciting photoelectrons therein by incident photons, and emitting the photoelectrons generated and accelerated inside the photoelectric conversion layer from a photoelectron emission surface to the outside, and the semiconductor on the photoelectron emission surface. A surface electrode formed on a layer, and a back electrode formed on the semiconductor layer opposite to the photoelectron emission surface on the semiconductor layer so as to face the surface electrode. The surface electrode is divided into a plurality of pixels. The plurality of pixel electrodes are connected to a plurality of bias applying wires for independently applying a positive bias potential compared to the back electrode. Further, inside the vacuum container, a plurality of switch elements for individually switching bias application by individually turning on and off the connection between the plurality of bias application wirings and the plurality of pixel electrodes, and A switching circuit for individually turning on and off a plurality of switching elements, and a plurality of switching wirings for individually connecting a plurality of output terminals of the switching circuit to individual control terminals of the plurality of switching elements, The timing control means, when a start signal is given, continuously applies a timing pulse to the switching circuit, and the switching circuit sequentially turns on and off the plurality of switch elements in response to the timing pulse, The memory means starts a storage operation when the start signal is given, and sequentially becomes capable of emitting photoelectrons based on the timing pulse. A photodetector, wherein the output of the anode is stored in correspondence with the position of the pixel electrode.